Air assist fuel injectors and method of assembling air assist fuel injectors

ABSTRACT

A first air assist fuel injector configured for operation with a two stroke engine and a second air assist fuel injector configured for operation with a four stroke engine. The first air assist fuel injector and the second air assist fuel injector share one or more common items, such as a solenoid coil assembly and/or an armature, even though the air assist fuel injectors are configured for different applications.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to air assist fuel injectors, and,more particularly, to an assembly of air assist fuel injectors and amethod of assembling air assist fuel injectors.

[0003] 2. Description of the Related Art

[0004] Conventional fuel injectors are configured to deliver a quantityof fuel to a combustion cylinder of an engine. To increase combustionefficiency and decrease pollutants, it is desirable to atomize thedelivered fuel. Generally speaking, atomization of fuel can be achievedby supplying high pressure fuel to conventional fuel injectors, oratomizing low pressure fuel with pressurized gas, i.e., “air assist fuelinjection.”

[0005]FIG. 1 illustrates a conventional air assist fuel injector 20mounted to an air/fuel rail 30. The rail 30 houses a conventional fuelinjector 40 and also defines a mount for the air assist fuel injector20. The conventional fuel injector 40 and the fuel rail 30 areconfigured such that a metered quantity of fuel is delivered from thefuel injector to the air assist fuel injector 20. Additionally, the rail30 includes a number of passageways 42 that deliver pressurized air tothe air assist fuel injector 20. The air assist fuel injector 20atomizes the low pressure fuel with the pressurized air and conveys theair and fuel mixture to the combustion chamber of an engine (notillustrated).

[0006] As illustrated in FIG. 1, the pressurized air from the air/fuelrail 30 and the metered quantity of fuel from the conventional fuelinjector 40 enter the air assist fuel injector 20 through an inlet inthe center of an armature 26. Thereafter, the fuel and air travelthrough the interior of a poppet 24, and exit the poppet through smallslots near the end or head of the poppet. The poppet 24 is attached tothe armature 26, which is actuated by energizing a solenoid 22. When thesolenoid 22 is energized, the armature 26 will overcome the force of aspring 28 and move toward a leg 30. Because the poppet 24 is attached tothe armature, the head of the poppet will lift off a seat 32 so that ametered quantity of atomized fuel is delivered to the combustion chamberof an engine.

[0007] The configuration of two and four stroke engines dictate theexternal dimensions of the air assist fuel injector 20. Conventionally,separate air assist fuel injectors are manufactured for two and fourstroke engine applications to satisfy the different dimensionalrequirements of the two applications. For example, two stroke enginesoften require a shorter air assist fuel injector than that required forfour stroke engine applications because of strict space constraintsdirectly over the head of the two stroke engine. In contrast, fourstroke engine applications often require a narrower air assist fuelinjector than that required for two stroke engine applications becauseof strict space constraints in and around the head of the four strokeengine. Additionally, four stroke engine applications often require alonger air assist fuel injector than that required for two stroke engineapplications because the air assist fuel injector must extend into thecam valley, but avoid the valve components and any water passageways.Hence, two stroke engine applications have very tight heightrestrictions, requiring short air assist fuel injectors, while fourstroke engine applications have very tight diameter restrictions,requiring long and very small diameter air assist fuel injectors.

[0008] Because of these different dimensional requirements, a single,one-size, air assist fuel injector unfortunately cannot satisfy both twostroke and four stoke commercial applications. Hence, conventional airassist fuel injectors for two stroke engine applications and four stokeengine applications are independently manufactured and thus do not sharecommon parts, especially solenoids. For more than a decade, thisconstraint has proven to be particularly problematic in attempts toeconomically manufacture air assist fuel injectors for both two and fourstroke applications.

SUMMARY

[0009] In light of the previously described problems associated withmanufacturing conventional air assist fuel injectors, one object of themany embodiments of the present invention is to provide air assist fuelinjectors for both two and four stroke engines that have one or morecommon parts but also satisfy the dimensional and functionalrequirements of these applications.

[0010] In furtherance of this object, an additional aim of the manyembodiments of the present invention is to provide methods of assemblingair assist fuel injectors with one or more common parts for both two andfour stroke engine applications.

[0011] Other objects, advantages and features associated with theembodiments of the present invention will become more readily apparentto those skilled in the art from the following detailed description. Aswill be realized, the invention is capable of other and differentembodiments, and its several details are capable of modification invarious obvious aspects, all without departing from the invention.Accordingly, the drawings and the description are to be regarded asillustrative in nature, and not limitative.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a partial cross-sectional view of a conventional airassist fuel injector mounted to a conventional air/fuel rail housing aconventional fuel injector.

[0013]FIG. 2 is a side view of an air assist fuel injector configuredfor a two stroke engine application in accordance with one embodiment ofthe present invention.

[0014]FIG. 3 is a top view of the air assist fuel injector illustratedin FIG. 2.

[0015]FIG. 4 is a rear view of the air assist fuel injector illustratedin FIG. 2.

[0016]FIG. 5 is a cross-sectional view of the air assist fuel injectorillustrated in FIG. 2 taken along the line 5-5 in FIG. 4.

[0017]FIG. 6 is a side view of an air assist fuel injector configuredfor a four stroke engine application in accordance with one embodimentof the present invention.

[0018]FIG. 7 is a top view of the air assist fuel injector illustratedin FIG. 6.

[0019]FIG. 8 is a rear view of the air assist fuel injector illustratedin FIG. 6.

[0020]FIG. 9 is a cross-sectional view of the air assist fuel injectorillustrated in FIG. 6 taken along the line 9-9 in FIG. 8.

[0021]FIG. 10 is an exploded view of FIG. 5.

[0022]FIG. 11 is an exploded view of FIG. 9.

[0023]FIG. 12 is an exploded assembly view of the air assist fuelinjector illustrated in FIG. 2.

[0024]FIG. 13 is an exploded assembly view of the air assist fuelinjector illustrated in FIG. 6.

[0025]FIG. 14 is a partial cross-sectional view of the air assist fuelinjector illustrated in FIG. 2 located in the head of a two strokeinternal combustion engine.

[0026]FIG. 15 is a partial cross-sectional view of the air assist fuelinjector illustrated in FIG. 6 located in the head of a four strokeinternal combustion engine.

[0027]FIG. 16 is a diagram illustrating one method of assembling the airassist fuel injector illustrated in FIG. 2 and/or the air assist fuelinjector illustrated in FIG. 6.

[0028]FIG. 17 is a diagram illustrating inventories of parts forassembling the air assist fuel injectors illustrated in FIGS. 2 and 6 inaccordance with embodiments of the present invention.

[0029]FIG. 18 is a cross-sectional view of an alternative embodiment ofan air assist fuel injector configured for a two stroke application inaccordance with one embodiment of the present invention.

[0030]FIG. 19 is a cross-sectional view of an alternative embodiment ofan air assist fuel injector configured for a four stroke application inaccordance with one embodiment of the present invention.

DESCRIPTION OF SPECIFIC EMBODIMENTS

[0031] FIGS. 1-17 illustrate embodiments of air assist fuel injectors100, 100′. The air assist fuel injector 100 is configured for a twostroke internal combustion engine, while the air assist fuel injector100′ is configured for a four stroke internal combustion engine. Asdescribed further below, and contrary to conventional wisdom, the airassist fuel injectors 100, 100′ share a number of identical parts,greatly simplifying and economizing the commercial manufacture of thetwo air assist fuel injectors 100, 100′ as compared to conventional airassist fuel injectors configured for the same applications. Because theair assist fuel injectors 100, 100′ are functionally similar and share anumber of similar parts, like numbered parts of the injector 100 referto like numbered parts of the injector 100′ in the description thatfollows.

[0032] FIGS. 2-5, 10, 12, and 14 illustrate the components of the airassist fuel injector 100, which is configured for operation with atwo-stroke internal combustion engine. FIGS. 6-8, 11, 13, and 15illustrate the components of the air assist fuel injector 100′, which isconfigured for operation with a four-stroke internal combustion engine.FIG. 18 illustrates an alternative embodiment of an air assist fuelinjector 100″ configured for operation with a two-stroke internalcombustion engine, and FIG. 19 illustrates an alternative embodiment ofan air assist fuel injector 100′″ configured for operation with afour-stroke internal combustion engine.

[0033] For purposes of comparison FIGS. 2 and 6 illustrate the airassist fuel injectors 100, 100′ at the same dimensional scale; FIGS. 3 5and 7 9 illustrate the air assist fuel injectors 100, 100′ at the samedimensional scale; FIGS. 10 and 11 illustrate the air assist fuelinjectors 100, 100′ at the same dimensional scale; FIGS. 12 and 13illustrate the air assist fuel injectors 100, 100′ at the samedimensional scale; and FIGS. 18 and 19 illustrate the air assist fuelinjectors 100″, 100′″ at the same dimensional scale.

[0034] As is apparent by comparing FIGS. 2-5 with FIGS. 6-8, theexternal dimensions, i.e., periphery, of the air assist fuel injectors100, 100′ are significantly different. This is because two stroke andthe four stroke internal combustion engines dictate differentdimensional requirements for air assist fuel injectors. For example, thedimensions of a two stroke internal combustion engine typically requirethat the air assist fuel injector 100 be shorter or more compact thanthat required for a four stroke internal combustion engine. Likewise,the dimensions of a four stroke internal combustion engine typicallyrequire that the air assist fuel injector 100′ be longer and have asmaller diameter than that required for a two stroke internal combustionengine. Hence, as illustrated by comparing FIGS. 2 and 6, the air assistfuel injector 100 is generally more compact, i.e., shorter, than the airassist fuel injector 100′ as measured along a longitudinal axis y, y′ ofeach air assist fuel injector 100, 100′. Accordingly, the air assistfuel injector 100′ has a longer length L′ as measured along thelongitudinal axis y′ of the air assist fuel injector 100′ than thelength L of the air assist fuel injector 100 as measured along thelongitudinal axis y, y′ of the air assist fuel injector 100. Asdescribed further below, various components of the air assist fuelinjectors 100, 100′ contribute to the overall length L, L′ of the airassist fuel injectors. The items, i.e., components or parts, of the airassist fuel injectors 100, 100′ are now briefly described, followed byan explanation of the operation of the air assist fuel injectors, andthen a description of the assembly of the air assist fuel injectors.

[0035] The air assist fuel injectors 100, 100′ are configured to utilizepressurized gas to atomize low pressure liquid fuel, which togethertravel through the respective air assist fuel injectors 100, 100′ alonga direction of flow f, f′, as indicated in FIGS. 2 and 6. As bestillustrated by FIGS. 10 and 11, the air assist fuel injectors 100, 100′each include two primary assemblies: a solenoid assembly 110, 110′ and avalve assembly 160, 160′. The air assist fuel injectors 100, 100′ alsoeach include a cap 200, 200′ that defines an inlet to the air assistfuel injector for the pressurized gas and liquid fuel. Each cap 200,200′ includes at least one fuel passageway 210, 210′ that receivesliquid fuel and at least one gas passageway 212, 212′ that receivespressurized gas. In the preferred embodiment of the respective airassist fuel injectors 100, 100′, each cap 200, 200′ includes only onecylindrical liquid fuel passageway 210, 210′ located along the centeraxis of the cap, and four cylindrical gas passageways 212, 212′circumferentially and equally spaced about the respective liquid fuelpassageway 210, 210′. In alternative embodiments, the air assist fuelinjectors 100, 100′ do not include the respective caps 200, 200′ orinclude alternatively configured caps. For example, the liquid fuel andpressurized gas may enter each air assist fuel injector 100, 100′through an armature 172, 172′ of each air assist fuel injector, asopposed to the caps 200, 200′. Alternatively, each cap 200, 200′ mayinclude only one passageway that receives liquid fuel and pressurizedgas for eventual or immediate delivery to the interior of the respectiveair assist fuel injectors 100, 100′.

[0036] As illustrated by FIGS. 10-13, the solenoid assemblies 110, 110′each at least include a coil 114, 114′ of conductive wire wrapped arounda tubular bobbin 112, 112′. Each coil 114, 114′ preferably includes awinding of insulated conductor that is wound helically around therespective bobbin 112, 112′. The coils 114, 114′ each have two ends 116,116′ (see FIGS. 12 and 13) which are each electrically connected, suchas soldered, to a terminal 122, 122′. Each coil 114, 144′ is energizedby providing current to respective connectors 123, 123′, which areelectrically connected to the respective terminals 122, 122′.

[0037] Each coil 114, 114′ and bobbin 112, 112′ together define arespective solenoid coil assembly 120, 120′ of each respective solenoidassembly 110, 110′ (see FIGS. 12 and 13). The solenoid coil assembly120, 120′ of each solenoid assembly 110, 110′ is that portion of therespective solenoid assemblies that produces a magnetic field whenelectric current is applied to the respective coils 114, 114′. Asillustrated by FIGS. 12 and 13, the solenoid coil assembly 120 of theair assist fuel injector 100 and the solenoid coil assembly 120′ of theair assist fuel injector 100′ are identical, despite the fact that theair assist fuel injector 100 is configured for operation with a twostroke internal combustion engine and the air assist fuel injector 100′is configured for operation with an four stroke internal combustionengine. Because the solenoid coil assembly 120 and the solenoid coilassembly 120′ are identical, they are interchangeable between the twodifferently configured air assist fuel injectors 100, 100′.

[0038] In the preferred embodiments of the air assist fuel injectors100, 100′, the identical solenoid coil assemblies 120, 120′ arepre-manufactured such that they have the same shape, size and content.Each pre-manufactured and identical solenoid coil assembly 120, 120′includes the respective bobbin 112, 112′, coil 114, 114′, and ends 116,116′. Because the solenoid coil assemblies 120, 120′ are identical, thebobbin 112 and the bobbin 112′ are identical, the coil 114 and the coil114′ are identical, and the ends 116 and the ends 116′ are identical.

[0039] One reason why the solenoid coil assemblies 120, 120′ areidentical is because the Applicants discovered that a common solenoidcoil assembly 120, 120′ could satisfy the strict dimensionalrequirements of many two stroke engine and four stroke engineapplications, while still satisfying as the functional designrequirements of both applications. As illustrated in FIGS. 2 and 6, thisis achieved by each solenoid height h, h′ being small enough to fit bothtwo stroke and four stroke applications, and each solenoid diameter Ø,Ø′ being small enough to fit four stroke applications. In accordancewith one embodiment of the present invention, each solenoid height h, h′equals approximately 20 mm and each solenoid diameter Ø, Ø′ equalsapproximately 20 mm. Although these dimensions are preferred, it will berealized that other dimensions for each solenoid height h, h′ and eachsolenoid diameter Ø, Ø′ will also suffice, depending upon thedimensional and functional requirements of the specific two strokeengine and four stroke engine applications. Exemplary solenoid coilassemblies 120, 120′ suitable for the present invention include thosecommercially available from Trans Era, located in Ontario, Canada. Thepreferred identical solenoid coil assemblies 120, 120′ have thefollowing specifications: turns=189, wire gauge=27, and resistance=1.36Ohm. The normal applied operating voltage is, for example, approximately14 volts and the minimum operating voltage is approximately 6 volts.

[0040] Although each solenoid coil assembly 120, 120′ includes therespective bobbin 112, 112′, coil 114, 114′, and ends 116, 116′,alternative embodiments of the solenoid coil assemblies may includeother items of the solenoid assembly 110, 110′. For example, theidentical solenoid coil assemblies 120, 120′ may also include a casing118, 118′, one or more retainers 124, 124′, 126, 126′, or other items ofthe respective solenoid assemblies 110, 110′. Additionally, although thepreferred embodiments of each solenoid assembly 110, 110′ include theitems illustrated in FIGS. 10-13 and further described below, it will beappreciated that alternative embodiments of the solenoid assemblies 110,110′ may include more or less of these items, so long as each solenoidassembly includes a coil and a bobbin. For example, each solenoidassembly 110, 110′ may only include the respective coil 114, 114′ bobbin112, 112′ ends 116, 116′ and casing 118, 118′.

[0041] Each bobbin 112, 112′ of each solenoid coil assembly 120, 120′ isessentially a spool on which the conductor of the coil 114, 114′ iswound. Each bobbin 112, 112′ also defines a throughole 111, 111′ inwhich an armature 172, 172′ is electromagnetically actuated, as furtherdescribed below. Each bobbin 112, 112′ and coil 114, 114′ are located atleast partially within a tubular casing 118, 118′ of soft magneticsteel. Hence, the respective tubular casing 118, 118′ at least partiallyencases the respective coil 114, 114′. In the preferred embodiments, therespective casings 118, 118′ are identical such that they have the sameshape, size and content.

[0042] The solenoid assemblies 110, 110′ also each include an upperretainer 126, 126′ and a lower retainer 124, 124′, which are annularbodies that partially close-off the ends of the casing 118, 118′. Eachupper retainer 126, 126′ and each lower retainer 124, 124′ include acylindrical passageway coincident with the respective throughole 111,111 ′ of the corresponding bobbin 112, 112′. The retainers 126, 126′,124, 124′ of each solenoid assembly 110, 110′ retain the respectivebobbin 112, 112′ and coil 114, 114′ in the respective casing 118, 118′.The cylindrical passageway of each upper retainer 126, 126′ receives atleast a portion of the respective cap 200, 200′. Each cap 200, 200′ ispreferably press fit into the respective armature guide 168, 168′. Thecylindrical passageway of each lower retainer 124, 124′ receives atleast a portion of the respective valve assembly 160, 160′. Eachsolenoid assembly 110, 110′ also includes an overmold 128, 128′ ofinsulative material, such as glass-filled nylon, that houses therespective casing 118, 118′ and at least a portion of the respectiveupper and lower retainers 126, 126′, 124, 124′. The respective overmolds128, 128′ also house the terminals 122, 122′ and a portion of theconnectors 123, 123′, as illustrated in FIGS. 10 and 11.

[0043] Referring again to FIGS. 10 and 11, the valve assembly 160, 160′of each air assist fuel injector 100, 100′ defines the dynamic portionof the air assist fuel injector that functions as a valve to deliver theatomized quantity of liquid fuel and gas. As illustrated in FIGS. 10 and11, the preferred embodiments of the valve assemblies 160, 160′ eachinclude an armature 172, 172′, a poppet 162, 162′, a seat 164, 164′, aleg 166, 166′, a spring 170, 170′, and an armature guide 168, 168′. Thearmatures 172, 172′ are each formed of a ferromagnetic material, such as430 FR stainless steel or similar, and each function as the moving partof an electromagnetic actuator, defined by each solenoid coil assembly120, 120′ and respective armature 172, 172′ combination. Each armatureweighs approximately 3.91 grams. As illustrated in FIGS. 5 and 9, eacharmature 172, 172′ of the respective air assist fuel injector 100, 100′is located relative to the respective solenoid coil assembly 120, 120′such that each armature is subject to the lines of flux generated by therespective solenoid coil assembly. Hence, each armature 172, 172′ isactuated when the respective solenoid coil assembly 120, 120′ isenergized. In the preferred embodiments, each armature 172, 172′ islocated partially within the respective throughole 111, 111′ of therespective bobbin 112, 112′.

[0044] Each armature 172, 172′ includes a passageway 180, 180′ thatconveys a mixture of liquid fuel and gas to a respective inlet 182, 182′of the respective poppet 162, 162′. In the preferred embodiment, thepassageway 180, 180′ of each armature 172, 172′ includes a conicalconduit extending from a first end of each armature 172, 172′ adjacentthe respective cap 200, 200′ to the respective inlet 182, 182′ of therespective poppet 162, 162′. Each inlet 182, 182′ is located at anapproximate midpoint along the length of the respective armature 172,172′. However, the passageways 180, 180′ may take other forms. Forexample, the passageways 180, 180′ may each be one cylindricalpassageway extending the entire length of each armature 172, 172′, aplurality of passageways, or other configurations, as will be apparent.

[0045] In the preferred embodiments, each armature 172, 172′ alsoincludes grooves 169, 169′ in the cylindrical exterior surface of therespective armature and grooves 173, 173′ in the bottom face of therespective armature. As illustrated in FIGS. 10-13, the grooves 169,169′ extend the entire length of the respective armature 172, 172′. Thegrooves 169, 169′, 173, 173′ serve to relieve any pressure differentialbetween an area upstream of the respective armature 172, 172′ and anarea downstream of the respective armature. The grooves 169, 169′, 173,173′ also help reduce surface adhesion between the respective armature172, 172′ and corresponding leg 166, 166′.

[0046] As illustrated by FIGS. 12 and 13, the armature 172 of the airassist fuel injector 100 and the armature 172′ of the air assist fuelinjector 100′ are identical, despite the fact that the air assist fuelinjector 100 is configured for operation with a two stroke internalcombustion engine and the air assist fuel injector 100′ is configuredfor operation with an four stroke internal combustion engine. That is,the armature 172 and the armature 172′ have the same shape and size, andare thus interchangeable between the two differently configured airassist fuel injectors 100, 100′.

[0047] Each poppet 162, 162′ is attached to the corresponding armature172, 172′, which is actuated by energizing the solenoid coil assembly120, 120′. As illustrated in FIGS. 10 and 11, in the preferredembodiments, each armature 172, 172′ includes a cylindrical passagewaylocated downstream of the respective passageways 180, 180′ and thatmatingly receives a first end portion 184, 184′ of the respectivepoppets 162, 162′. Hence, each inlet 182, 182′ is located immediatelydownstream of the respective passageway 180, 180′ with respect to thedirection of flow f, f′ of the mixture of liquid fuel and gas. In thepreferred embodiments, the end portion 184, 184′ of the respectivepoppets 162, 162′ are each attached to the respective armatures 172,172′ with a welded connection, preferably a YAG laser weld. However,alternative attachments are also contemplated. For example, the poppet162, 162′ may be attached to the armature 172, 172′ at any variety oflocations with an interference fit, an adhesive, a threaded or screwedattachment, a lock and key attachment, a retaining ring attachment, anelectron beam weld, an ultrasonic weld, or other known attachments.Because each poppet 162, 162′ is attached to the respective armature172, 172′, each poppet 162, 162′ will move with the armature when thearmature is actuated by energizing the solenoid assembly 110, 110′. Inalternative embodiments, each passageway 180, 180′ extends between theupstream end face and the opposing, downstream end face of therespective armature 172, 172′, i.e., the entire length of the respectivearmature, and the first end portion 184, 184′ of the each poppet isattached to the respective armature at the downstream end face of thecorresponding armature.

[0048] Each poppet 162, 162′ is an elongated hollow tube for conveyingthe mixture of liquid fuel and pressurized gas, and each include a stem163, 163′ (see FIGS. 12 and 13) and a head 174, 174′. Each inlet 182,182′ of each poppet 162, 162′ opens into a tubular passageway 178, 178′,which extends from the inlet 182, 182′ to outlets 176, 176,′ which arelocated just prior to the respective head 174, 174′ of each poppet. Inthe preferred embodiments, each poppet 162, 162′ includes fourslot-shaped outlets 176, 176′ that are equally spaced from each otherand located approximately transverse to the longitudinal axis of thepoppet. Although preferred that each poppet 162, 162′ have fourslot-shaped outlets 176, 176′, other configurations will suffice. Forexample, each poppet 162, 162′ may include one slot shaped outlet, twocircular outlets, five oval outlets, or ten pin sized outlets.

[0049] Each head 174, 174′ is located downstream of the respectiveoutlets 176, 176′ and is roughly mushroom shaped with a conical orangled face that seats against the seat 164, 164′ when the solenoidassembly is not energized. When each armature 172, 172′ is actuated byenergizing the respective solenoid coil assembly 120, 120′, therespective poppet 162, 162′ moves with the corresponding armature suchthat the respective head 174, 174′ is lifted off the corresponding seat164, 164′ in a direction away from the air assist fuel injector. Whenthe respective head 174, 174′ is lifted off the corresponding seat 164,164′, a seal is broken between the respective head and seat such thatliquid fuel and gas exiting the respective outlets 176, 176′ exits eachair assist fuel injector 100, 100′.

[0050] As also illustrated in FIGS. 10 and 11, movement of each poppet162, 162′ is guided at a bearing 175, 175′ between the respective poppet162, 162′ and the corresponding seat 164, 164′. Each bearing 175, 175′is located just prior to the outlets 176, 176′ with respect to thedirection of flow f, f′ of the liquid fuel and gas through the injector.Hence, each poppet 162, 162′ and each seat 164, 164′ include a bearingsurface for guiding movement of the poppet near the head end of eachpoppet 162, 162′. Because each seat 176, 176′ serves as a bearing forpoppet movement and also absorbs the impact of the respective head 174,174′ when the poppet valve assembly 160, 160′ opens and closes, the seatis preferably fabricated from a wear and impact resistant material, suchas hardened 440 stainless steel. It will be appreciated that the airassist fuel injectors 100, 100′ need not include a separate seat. Forexample, each leg 166, 166′ may define the respective seat 164, 164′ andbearing 175, 175′.

[0051] The poppets 162, 162′ are elongated because when installed, theair assist fuel injectors 100, 100′ each protrude through the head of anengine to reach a combustion chamber. As is illustrated in FIGS. 12 and13, a length l of the poppet 162 of the air assist fuel injector 100 isless than a length l′ of the poppet 162′ of the air assist fuel injector100′. The poppet 162′ of the air assist fuel injector 100′ is longerthan the poppet 162 of the air assist fuel injector 100 because the airassist fuel injector 100′ is configured for operation with a four strokeinternal combustion engine, which generally requires that the air assistfuel injector 100′ extend into a cam valley of the four stroke engine.Because two stroke engines generally do not have an elaborate cam valleyas do four stroke engines, it is not necessary that the poppet 162 be aslong as the poppet 162′. Moreover, it is preferable that the air assistfuel injector 100, and hence the poppet 162, be as short as possiblebecause of the strict space constraints directly over the head of twostroke engines.

[0052] As further illustrated in FIGS. 10 and 11, each poppet 162, 162′moves within the elongated channel 165, 165′ of the respective leg 166,166′. Each leg 166, 166′ is an elongated body through which therespective poppet 162, 162′ moves and which supports the respective seat164, 164′. The interior channel of each leg 166, 166′ through which therespective poppet 162, 162′ moves may also serve as a secondary flowpath for the pressurized gas. Hence, when each head 174, 174′ lifts offthe respective seat 164, 164′, pressurized gas flows outside therespective poppet but inside the leg 166, 166′ to help atomize theliquid fuel and gas exiting the respective outlets 176, 176′. Asillustrated in FIGS. 10-13, each leg 166, 166′ has a different lengthfor the same reasons set forth above in regard to the poppets 162, 162′.Poppet 162 weighs approximately 1.4 grams and poppet 162′ weighsapproximately 2.82 grams.

[0053] The spring 170, 170′ of each valve assembly 160, 160′ is locatedbetween the respective armature 172, 172′ and leg 166, 166′. Moreparticularly, each spring 170, 170′ sits within a recessed bore 171,171′ that is concentric with the elongated channel 165, 165′ of the leg.Each bore 171, 171′ faces the respective armature 172, 172′ and definesa seat for the corresponding spring 170, 170′. Each spring 171, 171′ isa compression spring having a first end that abuts the respectivearmature 172, 172′ and a second end that abuts the respective leg 166,166′. The bottom of each bore 171, 171′ defines the seat for thedownstream end of the respective spring 170, 170′ and a recess 183, 183′defines a seat for the upstream end of the respective spring. The spring170, 170′ functions to bias the respective armature 172, 172′ away fromthe respective leg 166, 166′. When the solenoid coil assembly 120, 120′is not energized, each spring 170, 170′ biases the respective armature172, 172′ away from the respective leg 166, 166′ and thus thecorresponding poppet 162, 162′ is maintained in a closed position wherethe respective head 174, 174′ abuts against the corresponding seat 164,164′. However, when each solenoid coil assembly 120, 120′ is energized,the electromagnetic force causes the respective armature 172, 172′ toovercome the biasing force of the corresponding spring 170, 170′ suchthat the armature moves toward the leg until it abuts a stop surface167, 167′ of the respective leg 166, 166′. When the solenoid coilassembly 120, 120′ is deenergized, the electromagnetic force is removedand the respective spring 170, 170′ again forces the correspondingarmature 172, 172′ away from the respective stop surface 167, 167′.

[0054] As illustrated by FIGS. 12 and 13, the spring 170 of the airassist fuel injector 100 and the spring 170′ of the air assist fuelinjector 100′ are identical, despite the fact that the air assist fuelinjector 100 is configured for operation with a two stroke internalcombustion engine and the air assist fuel injector 100′ is configuredfor operation with a four stroke internal combustion engine. That is,the spring 170 and the armature 170 have the same shape and size, andare thus interchangeable between the two differently configured airassist fuel injectors 100, 100′. In the preferred embodiments, thesprings 170, 170′ have the following specifications: Spring Rate=3.1N/mm; Load at 8.24 mm =13.80 N±0.5 N.

[0055] As also illustrated in FIGS. 10 and 11, movement of each armature172, 172′ is guided by a bearing 161, 161 ′ between the respective outersurface of each armature and the inner surface of the correspondingarmature guide 168, 168′. The armature guide 168, 168′ is essentially atube that extends at least a portion of the length of the respectivearmature 172, 172′ to act as a guide for the armature. In the preferredembodiments, each armature guide 168, 168′ has a first end 151, 151′located upstream of the respective armature 172, 172′ with respect tothe direction of flowf f, f′ and a second end 153, 153′ locateddownstream of the armature with respect to the direction of flow f f′such that each armature guide 168, 168′ also seals the solenoid coilassembly 120, 120′ from the liquid fuel and gas flowing through thevalve assembly 160, 160′. Hence, the second end 153, 153′ of eacharmature guide 168, 168′ is sealingly attached to the respective leg,166, 166′ such as by a laser weld or otherwise, and the outer surface ofeach armature guide near the respective first end 151, 151′ serves as asealing surface for an upper seal 202, 202′ (see FIGS. 5 and 9). Thisarrangement helps prevent any liquid fuel and gas from exiting the airassist fuel injectors 100, 100′. Although the armature guide 168, 168′is preferred, it will be appreciated that the air assist fuel injectors100, 100′ need not include the armature guide. For example, a portion ofthe respective solenoid assembly 110, 110′ or a separate insert mayfunction as a guide for the respective armature 172, 172′. Additionally,the respective solenoid coil assembly 120, 120′ may be sealed from theliquid fuel and gas with multiple 0-rings, rather than with the aid ofeach armature guide 168, 168′, as will be apparent. Moreover, caps 200,200′ slidably engage each respective armature guide 168, 168′ whenassembled.

[0056] Although in the illustrated embodiment of each air assist fuelinjector 100, 100′ the armature guides 168, 168′ and other portions ofeach air assist fuel injector are not identical, it will be appreciatedthat alternative embodiments may include identical armature guides 168,168′, solenoid assemblies, and other parts. For example, FIG. 18illustrates an air assist fuel injector 100″ configured for operationwith a two stroke engine and FIG. 19 illustrates an air assist fuelinjector 100′″ configured for operation with a four stroke engine.Besides having identical solenoid coil assemblies, armatures 172″,172′″, and springs 170″, 170′″, the air assist fuel injectors 100″,100′″ also include identical armature guides 168″, 168′″, lower seals204″, 204′″, lower retainers 124″, 124′″, casings 118″,118′″, terminals122″,122′″, connectors 123″, 123′″ (not illustrated), overmolds 128″,128′″, upper retainers 126″, 126′″, upper seals 202″, 202′″ and caps200″, 200′″. The air assist fuel injector 100″ is identical in everyrespect to the air assist fuel injector 100, and the air assist fuelinjector 100′″ is identical in every respect to the air assist fuelinjector 100′, except that the armature guides 168″, 168′″, lower seals204″, 204′″, seats 164″, 164′″, lower retainers 124″, 124′″, casings118″,118′″, terminals 122″,122′″, connectors 123″, 123′″, overmolds128″, 128′″, upper retainers 126″, 126′″, upper seals 202″, 202′″ andcaps 200″. 200′″ of the respective air assist fuel injectors 100″, 100′″are also identical, whereas these parts are not identical in air assistfuel injectors 100, 100′. Hence, the respective poppets 162″, 162′″,legs 166″, 162′″, carbon damns 206″, 206′″, and seats 164″, 164′″ arethe only parts that are not identical in the air assist fuel injectors100″, 100′″. In alternative embodiments, the air assist fuel injectors100″, 100′″ also have identical seats. As will be apparent, thedescription of the air assist fuel injectors 100, 100′ and thedescription of the method of assembling the air assist fuel injectors100, 100′ is equally applicable to the air assist fuel injectors 100″,100′″.

[0057] The air assist fuel injectors 100, 100′ utilize pressurized airto atomize low pressure fuel. When installed in an engine, the airassist fuel injectors 100, 100′ are located such that the atomized lowpressure fuel that exits the air assist fuel injectors is delivered tothe internal combustion-chamber of an engine, i.e., the part of anengine in which combustion takes place, normally the volume of thecylinder between the piston crown and the cylinder head, although thecombustion chamber may extend to a separate cell or cavity outside thisvolume. For example, as illustrated by FIGS. 14 and 17, the air assistfuel injector 100 is located in a cavity 704 of a two stroke internalcombustion engine head 702 such that the air assist fuel injector candeliver a metered quantity of atomized liquid fuel to a combustioncylinder 703 of the two stroke internal combustion engine 700, where itis ignited by a spark plug or otherwise. Likewise, as illustrated byFIGS. 15 and 17, the air assist fuel injector 100′ is located in acavity 704′ of a four stroke internal combustion engine head 702′ suchthat the air assist fuel injector can deliver a metered quantity ofatomized liquid fuel to a combustion cylinder 703′ of a four strokeinternal combustion engine 700′, where it is ignited by a spark plug orotherwise.

[0058] As illustrated by FIGS. 14, 15, and 17 the air assist fuelinjectors 100, 100′ are each located adjacent a conventional fuelinjector 600, 600′. The fuel injector 600 is located at least partiallyin a cavity of an air/fuel rail 500 configured for the two stroke engine700, and the fuel injector 600′ is located at least partially in acavity of an air/fuel rail 500′ configured for the four stroke engine700′. Examples of fuel injectors 600, 600′ that are suitable fordelivering liquid fuel to the air assist fuel injectors include any topor bottom feed manifold port injector, commercially available fromBosch, Siemens, Delphi, Nippondenso, Keihen, Sagem, or Magneti Morelli.The air/fuel rails 500, 500′ each include one or more internalpassageways or external lines (not illustrated) that deliver liquid fuelto the respective fuel injector 600, 600′, as well as one or morepassageways 502, 502′ that deliver pressurized gas, preferably air, tothe respective air assist fuel injector 100, 100′.

[0059] The air assist fuel injectors 100, 100′ are termed “air assist”fuel injectors because each preferably utilizes pressured air to atomizeliquid fuel. In the preferred embodiments, the pressure of the air is atroughly 550 KPa for two stroke applications and at roughly 650 KPa forfour stroke applications, while the pressure of the liquid fuel isroughly between 620-800 KPa. Although it is preferred that the airassist fuel injectors atomize liquid gasoline with pressurized airdelivered by the air/fuel rail, it will be realized that the air assistfuel injectors 100, 100′ may atomize many other liquid combustible formsof energy with any variety of gases. For example, the air assist fuelinjectors 100, 100′ may atomize liquid kerosene or liquid methane withpressurized gaseous oxygen, propane, or exhaust gas. Hence, the term“air assist” is a term of art, and as used herein is not intended todictate that the air assist fuel injectors 100, 100′ be used only withpressurized air.

[0060] Each rail 500, 500′ also defines a mount for the respective airassist fuel injector 100, 100′. That is, the respective air/fuel rail500, 500′ abuts against at least one surface of the respective airassist fuel injector 100, 100′ to retain the air assist fuel injector inplace in the respective cavities 704, 704′ of the respective heads 500,500′. In an alternative embodiment not illustrated, an o-ring defines aseal between the air assist fuel injector and the air/fuel rail. Such ano-ring may be considered part of the air assist fuel injector 100 or theair/fuel rail 202. The conventional fuel injectors 600, 600′ areconfigured and located such that they each deliver a metered quantity ofliquid fuel directly to the inlet at the respective cap 200, 200′ of theair assist fuel injectors 100, 100′. Hence, each cap 200, 200′ receivesthe pressurized gas from the respective air/fuel rail 500, 500′ as wellas the liquid fuel from the respective conventional fuel injector 600,600′. Because of the proximity of the outlet of the respective fuelinjector 600, 600′ with respect to the respective cap 200, 200′, themajority of the liquid fuel exiting from the respective fuel injector600, 600′ will enter the respective fuel passageway 210, 210′ (see FIGS.10 and 11). The pressurized gas is delivered to the respective cap 200,200′ via an annular passageway 501, 501′ in the respective air/fuel rail500, 500′. The majority of the pressurized gas conveyed by therespective air/fuel rail 500, 500′ will thus enter the gas passageways212, 212′ of the corresponding cap 200, 200′. Hence, each cap 200, 200′functions as an inlet to the respective air assist fuel injector 100,100′ for the pressurized gas and liquid fuel.

[0061] The pressurized gas and the liquid fuel mixture exits therespective cap 200, 200′ and then enters the respective armature 172,172′ located immediately downstream of the corresponding cap withrespect to the direction of flow f, f′. The liquid fuel and pressurizedgas mix in the respective passageway 182, 182′ of each armature 172,172′ and are conveyed to the respective inlet 182, 182′ of each poppet162, 162′. Thereafter, the liquid fuel and gas travel through therespective tubular passageway 178, 178′ of each poppet 162, 162′. Whenthe solenoid coil assemblies 120, 120′ are energized, the respectivearmature 172, 172′ overcomes the biasing force of the respective spring170, 170′ and moves toward the corresponding leg 166, 166′ until itseats against the respective stop surface 167, 167′. Because each poppet162, 162′ is attached to the respective armature 172, 172′, each head174, 174′ of the respective poppet lifts off of the seat in thedirection of flow f, f′when the respective armature is actuated. Wheneach head 174, 174′ lifts off of the respective seat 164, 164′, a sealbetween the head and the seat is broken and the gas and fuel mixtureexits the outlets 176, 176′. The mixture exiting each set of outlets176, 176′ is then forced out of each air assist injector 100, 100′ overthe respective head 174, 174′ such that a metered quantity of atomizedliquid fuel is delivered to the respective combustion chamber 703, 703′.

[0062] When the previously described solenoid coil assembly 120, 120′ isdeenergized, the biasing force of the respective spring 170, 170′returns the armature 172, 172′ to its original position. Because eachpoppet 162, 162′ is attached to the respective armature 172, 172′, thecorresponding head 174, 174′ of each poppet 162, 162′ returns to therespective seat 164, 164′ to define a seal that prevents further gas andfuel from exiting the respective air assist fuel injector 100, 100′.Hence, the air assist fuel injectors 100, 100′ each atomize the liquidfuel supplied by the respective conventional fuel injector 600, 600′with the pressurized gas supplied via the respective air/fuel rail 500,500′. The atomized fuel is then delivered to the respective combustionchamber 703, 703′ of the respective engine 700, 700′, where it isignited to power the respective engine 700, 700′.

[0063] One preferred embodiment of assembling the air assist fuelinjector 100 is now described in reference to FIGS. 12, 13, 16, and 17.As will be appreciated, the following assembly method is applicable tothe air assist fuel injector 100 as well as the air assist fuel injector100′. Hence, the following description of one method of assembling theair assist fuel injector 100 is also one method of assembling the airassist fuel injector 100′. As illustrated by FIG. 16, the assemblyprocess begins by assembling the valve assembly 160 or the solenoidassembly 110. The valve assembly 160 may also be assembled in parallelwith the solenoid assembly 110, i.e., at the same time.

[0064] First, considering the assembly of the valve assembly 160, at astep 1000, the armature guide 168 is fitted to the leg 166, preferablyby press-fitting the armature guide 168 onto the reduced portion of theleg 166, at the upstream end of the leg 166. Thereafter, at a step 1002,the armature guide 168 and leg 166 combination are placed onto afixture, such as a rotatable chuck, collet, sleeve, ferrule, etc. At astep 1004, the seat 164 is fitted to the leg 166, preferably byslip-fitting the seat 164 into a cavity in the downstream end of the leg166. As illustrated by FIG. 16, at a step 1006, the seat 164 and thearmature guide 168 are then attached to the leg 166, preferably by oneor more hermetic YAG laser welds, although other attachments are alsocontemplated as described earlier.

[0065] After the armature guide 168 and the seat 164 are attached to theleg 166 they are removed from the fixture, and, at a step 1008, theupstream end (seat side) of the poppet 162 is inserted into the tubularpassageway 178 of the leg 166 until the poppet head 174 abuts againstthe seat 164. At a step 1010, the spring 170 is then inserted into theannular area 171 between the poppet 162 and the interior surface of theleg 166 at the upstream end of the leg. Then, at a step 1012, thearmature 172 is fitted to the poppet, preferably by a press-fitting thearmature over the proximal end of the poppet 162. The armature 172 ispress-fit to such an extent that the armature compresses the spring 170and the armature abuts the stop surface 167 of the leg 166. At a step1014, a pin or rod is inserted into the passageway 180 of the armaturefrom the upstream side of the armature to push the poppet 162 back outof the armature 172 (in the direction of flow f) to set the stroke orlift of the armature, i.e., the amount of axial movement of the armatureduring operation. A dial indicator is used on the end of the poppet 162to measure the stroke during step 1014. After the stroke of the armature172, and thus the stroke of the poppet 162, are set at step 1014, theassembly of the valve assembly 160 is completed by attaching the poppet162 to the armature 172 at a step 1016, preferably by hermetically YAGlaser welding the armature to the poppet, roughly at the intersection orjoint between the passageway 180 and the inlet 182 of the poppet.

[0066] The assembly of the solenoid assembly 110 begins with assemblingthe solenoid coil assembly 120. At a step 1018, the solenoid coilassembly 120 is assembled by winding the conductor of the coil 114 onthe bobbin 112 and attaching the ends 116 to the coil. The coil 128 canoptionally be encapsulated in a insulative material after being wound onthe bobbin 112. At a step 1020, the solenoid coil assembly 120 isencased, preferably by pressing the lower retainer 124 into the solenoidcasing 118, placing the solenoid coil assembly 120 into the casing 118,pressing the top retainer 126 into the casing 118, and then welding theretainers 124, 126 to the casing 118. In the preferred embodiment, thesolenoid coil assembly 120 is preassembled, i.e., pre-manufactured, andthus the assembly of the solenoid assembly 110 begins at step 1020.

[0067] At a step 1022, the terminals 122 and/or the connectors 123 areattached to the ends 116. At a step 1024, the solenoid assembly 110 iscompleted by overmolding with the overmold 128. To perform the overmoldprocess retainers 124, 126 are welded to the casing 118. Connectors 123are then welded to terminals 122. Overmold 128 is formed by placing amold around the solenoid assembly 110. The mold die is placed around thesolenoid assembly 110 to form the geometry of overmold 128. Overmold 128encapsulates the outer diameter of solenoid assembly 110 and seals offaround connectors 123.

[0068] After the valve assembly 160 and the solenoid assembly 110 arecomplete, at a step 1026, the solenoid assembly is fitted to the valveassembly, preferably by pressing the solenoid assembly over the valveassembly. Then, at a step 1028, the solenoid assembly is attached to thevalve assembly, preferably by a laser weld. After the solenoid assembly110 and the valve assembly 160 are attached, the upper seal 202 isplaced over the upstream end of the sleeve guide 168 and then, at a step1030, the cap 200 is fitted to the remainder of the injector, preferablyby press-fitting the cap 200 into the upstream end of the armature guide168. To complete the assembly of the air assist fuel injector 200, at astep 1032, a lower seal 204 and a carbon dam 206 are positioned inplace. In the preferred embodiment, the lower seal 204 is a viton Oring, and the carbon dam 206 is a Teflon dam.

[0069] Although FIG. 16 illustrates the preferred method of assembly ofthe present invention, it will be appreciated that additional steps maybe added and some of the previously described steps may be removed inalternative embodiments of the present invention, depending upon thespecific configuration of the air assist fuel injector being assembled.Additionally, it will be appreciated that the order of the stepsillustrated in FIG. 16 can vary and still be within the confines of thepresent invention.

[0070] Because of the different configurations of the two strokeinternal combustion engine 700 and the four stroke internal combustionengine 700′, the air assist fuel injectors 100, 100′, as describedabove, have different external dimensions. Nevertheless, in accordancewith the embodiments of the present invention, the air assist fuelinjectors 100, 100′ are configured such that they share a number ofidentical parts. As illustrated in FIG. 17, these identical parts arestored in a common parts inventory 4000 when assembling the air assistfuel injectors 100, 100′ in the manner described above. When assemblingthe air assist fuel injectors 100, 100′, the common parts inventory 4000includes one or more of the following: (1) an inventory of identicalsolenoid coil assemblies 120, 120′; (2) an inventory of identicalarmatures 172, 172′; and (3) an inventory of identical springs 170,170′. The remainder of parts for the air assist fuel injector 100 thatare not held in the inventory 4000 are stored in a two stoke air assistfuel injector inventory 4002, and the remainder of parts for the airassist fuel injector 100′ that are not held in the inventory 4000 arestored in a four stroke air assist fuel injector inventory 4004. Hence,the two stroke air assist injector inventory 4002 for the two stroke airassist fuel injector 100 includes one or more of the following: carbondam 206, lower seal 204, seat 164, leg 166, armature guide 168, lowerretainer 124, casing 118, terminal 122, connector 123, overmold 128,upper retainer 126, upper seal 202, poppet 162, and cap 200. Likewise,the four stroke injector inventory 4004 for the four stroke air assistfuel injector 100′ includes one or more of the following: carbon dam206′, lower seal 204′, seat 164′, leg 166′, armature guide 168′, lowerretainer 124′, casing 118′, terminal 122′, connector 123′, overmold128′, upper retainer 126′, upper seal 202′, poppet 162′ and cap 200′.

[0071] Hence, when assembling the air assist fuel injector 100 asillustrated in FIG. 16, the solenoid coil assembly 120, the armature172, and the spring 170 are retrieved from the common parts inventory4000 and the remainder of the parts (carbon dam 206, lower seal 204,seat 164, leg 166, armature guide 168, lower retainer 124, casing 118,terminal 122, connector 123, overmold 128, upper retainer 126, upperseal 202, poppet 162 and cap 200) for the air assist fuel injector areretrieved from the two stroke air assist fuel injector inventory 4002.When assembling the air assist fuel injector 100′, the solenoid coilassembly 120′, the armature 172′, and the spring 170′ are retrieved fromthe common parts inventory 4000 and the remainder of the parts (carbondam 206′, lower seal 204′, seat 164′, leg 166′, armature guide 168′,lower retainer 124′, casing 118′, terminal 122′, connector 123′,overmold 128′, upper retainer 126′, upper seal 202′, poppet 162′ and cap200′ ) for the air assist fuel injector 100′ are retrieved from the fourstroke air assist fuel injector inventory 4004.

[0072] In alternative embodiments, the common parts inventory 4000 alsoincludes an inventory of one or more of the following: armature guides,casings, carbon dams, seats, lower retainers, upper retainers, and upperseals. For example, a common parts inventory for the air assist fuelinjectors 100″, 100′″ illustrated in FIGS. 18 and 19 includes identicalsolenoid coil assemblies, identical armatures 172″, 172′″, identicalsprings 170″, 170′″, identical armature guides 168″, 168′″, identicalcarbon dams 206″, 206″′, identical lower seals 204″, 204′″, identicallower retainers 124″, 124′″, identical casings 118″,118′″, identicalterminals 122″,122′″, identical connectors 123″, 123′″, identicalovermolds 128″, 128′″, identical upper retainers 126″, 126′″, identicalupper seals 202″, 202′″ and identical caps 200″, 200′″. Hence, whenassembling the air assist fuel injector 100″, the remainder of parts(seat 164″, leg 166″, and poppet 162″) for the air assist fuel injector100″ are retrieved from the two stroke air assist fuel injectorinventory. Likewise, when assembling the air assist fuel injector 100′″,the remainder of parts (seat 164′″, leg 166′″, and poppet 162′″) for theair assist fuel injector 100′″ are retrieved from the four stroke airassist fuel injector inventory.

[0073] As set forth above, the configuration of the two stroke engine700 and the four stroke engine 700′ dictate the external dimensions ofthe air assist fuel injectors 100, 100′. More specifically, two strokeengine applications have very tight height restrictions, requiring shortair assist fuel injectors, while four stroke engine applications havevery tight diameter restrictions, requiring long and very small diameterair assist fuel injectors. To satisfy the different dimensionalrequirements of these two applications, it was conventionally thought toseparately manufacture two different air assist fuel injectors having nocommon parts. However, as set forth above, the embodiments of thepresent invention strive to address this problem by providing air assistfuel injectors 100, 100′ that share a number of common parts, especiallythe solenoid coil assembly 120, 120′ and/or armature 172, 172′. Thesolenoid coil assemblies 120, 120′ satisfy the strict dimensionalrequirements of many two stroke engine and four stroke engineapplications, while still satisfying the functional design requirementsof the air assist fuel injectors 100, 100′ for both applications. Thatis, each solenoid height h, h′ is small enough to fit two stroke engineapplications, each solenoid diameter Ø, Ø′ is small enough to fit fourstroke applications, and the configuration of each solenoid assembly110, 110′ is sufficient to actuate the different length and weightarmature/poppet combinations of the two air assist fuel injectors 100,100′. Hence, the air assist fuel injector 100 is short enough to satisfytwo stroke engine applications and the air assist fuel injector 100′ islong and narrow enough to satisfy four stroke engine applications, whilethe solenoid assembly 110, 110′ of each air assist fuel injector issized and configured to fit both two stroke and four strokeapplications; this significantly simplifies the manufacture of the airassist fuel injectors 100, 100′ as compared to conventional air assistfuel injectors configured for the same applications.

[0074] The principles, preferred embodiments, and modes of operation ofthe present invention have been described in the foregoing description.However, the invention which is intended to be protected is not to beconstrued as limited to the particular embodiments disclosed. Further,the embodiments described herein are to be regarded as illustrativerather than restrictive. Variations and changes may be made by others,and equivalents employed, without departing from the spirit of thepresent invention. Accordingly, it is expressly intended that all suchvariations, changes and equivalents which fall within the spirit andscope of the present invention as defined in the claims be embracedthereby.

what is claimed is:
 1. An assembly of items comprising: a first airassist fuel injector configured for a two stroke internal combustionengine, said first air assist fuel injector having a solenoid assembly,a poppet, a poppet seat, and an armature attached to said poppet; and asecond air assist fuel injector configured for a four stroke internalcombustion engine, said second air assist fuel injector having asolenoid assembly, a poppet, a poppet seat, and an armature attached tosaid poppet of said second air assist fuel injector; said solenoidassembly of said first air assist fuel injector and said solenoidassembly of said second air assist fuel injector being identical, saidarmature of said first air assist fuel injector and armature of saidsecond air assist fuel injector being identical, said poppet of saidfirst air assist fuel injector being shorter than said poppet of saidsecond air assist fuel injector as measured along a longitudinal axis ofsaid poppet of said first air assist fuel injector and as measured alonga longitudinal axis of said poppet of said second air assist fuelinjector.
 2. An assembly of items comprising: a first air assist fuelinjector configured for a two stroke internal combustion engine, saidfirst air assist fuel injector having a solenoid assembly and a poppet,said poppet having a length as measured along a longitudinal axis ofsaid poppet; and a second air assist fuel injector configured for a fourstroke internal combustion engine, said second air assist fuel injectorhaving a solenoid assembly and a poppet, said poppet of said second airassist fuel injector having a length as measured along a longitudinalaxis of said poppet of said second air assist fuel injector, said lengthof said poppet of said first air assist fuel injector being shorter thansaid length of said poppet of said second air assist fuel injector, saidsolenoid assembly of said first air assist fuel injector and saidsolenoid assembly of said second air assist fuel injector beingidentical.
 3. The assembly of items of claim 2, said solenoid assemblyof said first air assist fuel injector and said solenoid assembly ofsaid second air assist fuel injector each including a casing and acylindrical coil of wire wound on a bobbin, said casing of said firstair assist fuel injector housing said cylindrical coil and said bobbinof said first air assist fuel injector, said casing of said second airassist of fuel injector housing said cylindrical and said bobbin of saidsecond air assist fuel injector.
 4. The assembly of items of claim 3,said solenoid assembly of first air assist fuel injector and saidsolenoid assembly of second air assist fuel injector each including anovermold, each of said overmolds having a height h of substantially 20millimeters and a diameter of substantially 20 millimeters.
 5. Theassembly of items of claim 3, said first air assist fuel injectorincluding an armature attached to said poppet of said first air assistfuel injector, said second air assist fuel injector including anarmature attached to said poppet of said second air assist fuelinjector, said armature of said first air assist fuel injector and saidarmature of said second air assist fuel injector being identical.
 6. Theassembly of items of claim 5, said first air assist fuel injector havingan armature guide for guiding movement of said armature of said firstair assist fuel injector, said armature guide having a first end locatedupstream of said armature of said first air assist fuel injector withrespect to a direction of flow of a mixture of liquid fuel and gasthrough said second air assist fuel injector and a second end locateddownstream of said armature of said first air assist fuel injector withrespect to said direction of flow of said mixture through said secondair assist fuel injector, said second air assist fuel injector having anarmature guide for guiding movement of said armature of said second airassist fuel injector, said armature guide of said second air assist fuelinjector guide having a first end located upstream of said armature ofsaid second air assist fuel injector with respect to a direction of flowof a mixture of liquid fuel and gas and a second end located downstreamof said armature of said second air assist fuel injector with respect tosaid direction of flow of said mixture, said armature guide of saidfirst air assist fuel injector and said armature guide of said secondair assist fuel injector being identical.
 7. The assembly of items ofclaim 2, in combination with said two stroke internal combustion engine.8. The assembly of items of claim 7, said two stroke internal combustionengine having a head, said head having an opening that receives at leasta portion of said first air assist fuel injector.
 9. The assembly ofitems of claim 2, in combination with said four stroke internalcombustion engine.
 10. The assembly of items of claim 9, said fourstroke internal combustion engine having a head, said head having anopening that receives at least a portion of said second air assist fuelinjector.
 11. An assembly of items comprising: a first air assist fuelinjector configured for a two stroke internal combustion engine, saidfirst air assist fuel injector having a poppet and an armature attachedto said poppet, said poppet having a length as measured along alongitudinal axis of said poppet; and a second air assist fuel injectorconfigured for a four stroke internal combustion engine, said second airassist fuel injector having a poppet and an armature attached to saidpoppet, said poppet of said second air assist fuel injector having alength as measured along a longitudinal axis of said poppet of saidsecond air assist fuel injector, said length of said poppet of saidfirst air assist fuel injector being shorter than said length of saidpoppet of said second air assist fuel injector, said armature of saidfirst air assist fuel injector and said armature of said second airassist fuel injector being identical.
 12. The assembly of items of claim11, said first air assist fuel injector having an armature guide forguiding movement of said armature of said first air assist fuelinjector, said armature guide having a first end located upstream ofsaid armature of said first air assist fuel injector with respect to adirection of flow of a mixture of liquid fuel and gas through said firstair assist fuel injector and a second end located downstream of saidarmature of said first air assist fuel injector with respect to saiddirection of flow of said mixture, said second air assist fuel injectorhaving an armature guide for guiding movement of said armature of saidsecond air assist fuel injector, said armature guide of said second airassist fuel injector guide having a first end located upstream of saidarmature of said second air assist fuel injector with respect to adirection of flow of a mixture of liquid fuel and gas through saidsecond air assist fuel injector and a second end located downstream ofsaid armature of said second air assist fuel injector with respect tosaid direction of flow of said mixture through said second air assistfuel injector, said armature guide of said first air assist fuelinjector and said armature guide of said second air assist fuel injectorbeing identical.
 13. The assembly of items of claim 11, in combinationwith said two stroke internal combustion engine.
 14. The assembly ofitems of claim 13, said two stroke internal combustion engine having ahead, said head having an opening that receives at least a portion ofsaid first air assist fuel injector.
 15. The assembly of items of claim11, in combination with said four stroke internal combustion engine. 16.The assembly of items of claim 15, said four stroke internal combustionengine having a head, said head having an opening that receives at leasta portion of said second air assist fuel injector.
 17. An assembly ofitems comprising: a first air assist fuel injector configured for a twostroke internal combustion engine, said first air assist fuel injectorhaving a poppet, an armature attached to said poppet, and an armatureguide for guiding movement of said armature, said armature guide havinga first end located upstream of said armature with respect to adirection of flow of a mixture of liquid fuel and gas through said firstair assist fuel injector and a second end located downstream of saidarmature with respect to said direction of flow of said mixture, saidpoppet having a length as measured along a longitudinal axis of saidpoppet; and a second air assist fuel injector configured for a fourstroke internal combustion engine, said second air assist fuel injectorhaving a poppet, an armature attached to said poppet of said second airassist injector, and an armature guide for guiding movement of saidarmature of said second air assist fuel injector, said armature guide ofsaid second air assist fuel injector guide having a first end locatedupstream of said armature of said second air assist fuel injector withrespect to a direction of flow of a mixture of liquid fuel and gasthrough said second air assist fuel injector and a second end locateddownstream of said armature of said second air assist fuel injector withrespect to said direction of flow of said mixture through said secondair assist fuel injector, said poppet of said second air assist fuelinjector having a length as measured along a longitudinal axis of saidpoppet of said second air assist fuel injector, said length of saidpoppet of said first air assist fuel injector being shorter than saidlength of said poppet of said second air assist fuel injector, saidarmature guide of said first air assist fuel injector and said armatureguide of said second air assist fuel injector being identical.
 18. Theassembly of items of claim 17, said armature of said first air assistfuel injector and said armature of said second air assist fuel injectorbeing identical.
 19. The assembly of items of claim 17, in combinationwith said two stroke internal combustion engine.
 20. The assembly ofitems of claim 19, said two stroke internal combustion engine having ahead, said head having an opening that receives at least a portion ofsaid first air assist fuel injector.
 21. The assembly of items of claim17, in combination with said four stroke internal combustion engine. 22.The assembly of items of claim 21, said four stroke internal combustionengine having a head, said head having an opening that receives at leasta portion of said second air assist fuel injector.
 23. A methodcomprising: keeping an inventory of identical solenoid assemblies;keeping an inventory of identical armatures; keeping an inventory ofidentical springs; keeping an inventory of first poppets having a firstlength; keeping an inventory of second poppets having a second length,the first length being different than the second length; assembling afirst air assist fuel injector for a two stroke internal combustionengine with one of the solenoid assemblies, one of the armatures, one ofthe springs, and one of the first poppets; and assembling a second airassist fuel injector for a four stroke internal combustion engine withanother of the solenoid assemblies, another of the armatures, another ofthe springs, and another of the second poppets.
 24. A method comprising:keeping an inventory of identical solenoid assemblies; keeping aninventory of first poppets having a first length; keeping an inventoryof second poppets having a second length, the first length beingdifferent than the second length; assembling a first air assist fuelinjector for a two stroke internal combustion engine with one of thesolenoid assemblies and one of the first poppets; and assembling asecond air assist fuel injector for a four stroke internal combustionengine with another of the solenoid assemblies and one of the secondpoppets.
 25. The method of claim 24, further comprising: keeping aninventory of identical armatures; said assembling the first air assistfuel injector including assembling the first air assist fuel injectorwith one of the armatures; and said assembling the second air assistfuel injector including assembling the second air assist fuel injectorwith another of the armatures.
 26. The method of claim 24, furthercomprising: keeping an inventory of identical armature guides; saidassembling the first air assist fuel injector including assembling thefirst air assist fuel injector with one of the armature guides; and saidassembling the second air assist fuel injector including assembling thesecond air assist fuel injector with another of the armature guides. 27.A method comprising: keeping an inventory of identical armatures;keeping an inventory of first poppets having a first length; keeping aninventory of second poppets having a second length, the first lengthbeing different than the second length; assembling a first air assistfuel injector for a two stroke internal combustion engine with one ofthe armatures and one of the first poppets; and assembling a second airassist fuel injector for a four stroke internal combustion engine withanother of the armatures and one of the second poppets.
 28. The methodof claim 27, further keeping an inventory of identical armature guides;said assembling the first air assist fuel injector including assemblingthe first air assist fuel injector with one of the armature guides; andsaid assembling the second air assist fuel injector including assemblingthe second air assist fuel injector with another of the armature guides.29. A method comprising: keeping an inventory of identical armatureguides; keeping an inventory of first poppets having a first length;keeping an inventory of second poppets having a second length, the firstlength being different than the second length; assembling a first airassist fuel injector for a two stroke internal combustion engine withone of the armature guides and one of the first poppets; and assemblinga second air assist fuel injector for a four stroke internal combustionengine with another of the armature guides and one of the secondpoppets.
 30. An assembly of items comprising: a first air assist fuelinjector configured for a two stroke internal combustion engine, saidfirst air assist fuel injector having a solenoid assembly and a poppet,said poppet having a length as measured along a longitudinal axis ofsaid poppet, said solenoid assembly having a diameter and a length asmeasured along a center axis of said solenoid assembly; and a second airassist fuel injector configured for a four stroke internal combustionengine, said second air assist fuel injector having a solenoid assemblyand a poppet, said poppet of said second air assist fuel injector havinga length as measured along a longitudinal axis of said poppet of saidsecond air assist fuel injector, said solenoid assembly of said secondair assist fuel injector having a diameter and a length as measuredalong a center axis of said solenoid assembly of said second air assistfuel injector, said length of said poppet of said first air assist fuelinjector being shorter than said length of said poppet of said secondair assist fuel injector, said diameter of said solenoid assembly ofsaid first air assist fuel injector being substantially the same as saiddiameter of second solenoid assembly of said second air assist fuelinjector, said length of said solenoid assembly of said first air assistfuel injector being substantially the same as said length of secondsolenoid assembly of said second air assist fuel injector.
 31. Theassembly of items of claim 30, said diameter of said solenoid assemblyof said first air assist fuel injector being 20 mm.
 32. The assembly ofitems of claim 31, said length of said solenoid assembly of said firstair assist fuel injector being 20 mm.
 33. The assembly of items of claim30, said length of said solenoid assembly of said first air assist fuelinjector being 20 mm.